Ultrafast optical generation and remote detection of terahertz sound using semiconductor superlattices

The authors introduce an all-optical approach to study the propagation of high frequency acoustic phonons in which the generation and detection involves two spatially separated superlattices ∼1μm apart. Propagating modes of frequencies up to ∼1THz escape from the superlattice where they are generated and reach the second superlattice where they are detected and spectrally resolved using pump-probe techniques. The measured frequency spectrum reveals finite size effects, which can be accounted for by a continuum elastic model.